/*
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.commons.discovery.resource.names;

import org.apache.commons.discovery.ResourceNameDiscover;
import org.apache.commons.discovery.ResourceNameIterator;


/**
 * Helper class for methods implementing the ResourceNameDiscover interface.
 * 
 * @author Richard A. Sitze
 */
public abstract class ResourceNameDiscoverImpl implements ResourceNameDiscover
{
    /**
     * Locate names of resources that are bound to <code>resourceName</code>.
     * 
     * @return ResourceNameIterator
     */
    public abstract ResourceNameIterator findResourceNames(String resourceName);

    /**
     * Locate names of resources that are bound to <code>resourceName</code>.
     * 
     * @return ResourceNameIterator
     */
    public ResourceNameIterator findResourceNames(final ResourceNameIterator inputNames) {
        return new ResourceNameIterator() {
            private ResourceNameIterator resourceNames = null;
            private String resourceName = null;
            
            public boolean hasNext() {
                if (resourceName == null) {
                    resourceName = getNextResourceName();
                }
                return resourceName != null;
            }
            
            public String nextResourceName() {
                String name = resourceName;
                resourceName = null;
                return name;
            }
            
            private String getNextResourceName() {
                while (inputNames.hasNext() && (resourceNames == null  ||  !resourceNames.hasNext())) {
                    resourceNames =
                        findResourceNames(inputNames.nextResourceName());
                }
    
                return (resourceNames != null  &&  resourceNames.hasNext())
                       ? resourceNames.nextResourceName()
                       : null;
            }
        };
    }
}